Apparatus for stirring molten metal



March 0- F. R. MULLEFI :1- AL 9 APPARATUS FOR STIRRING IOLTEN METAL Filed larch z, 1939 r 5 JNVENTORS IIEDER/c/(R M4455.

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M W M ATTORNEYS Patented Mar. 26, 1940 2,195,092

UNITED STATES PATENT OFFICE APPARATUS FOR STIBBING MOLTIIN METAL Frederick R. Muller, Carteret, and Walter '1. Monaco, Newark, N. 1., aulgnora to The American Metal Comp ny, Limited, New York, N. Y., a corporation of New York Application March 2, 1m, Serial in. 259,424 4 Claims. (crass- :4)

This invention relates to apparatus for stirring Fig. 2 is an enlarged elevatlonal view showing molten metal. an impeller for stirringmolten metal mounted In various processes for treating molten metal, upon the lower end of a rotatable shaft to which such for example as the rapid detinning of lead, a stabilizing device is applied in accordance with it is necessary to provide apparatus for stirring this invention; 5 large masses of the molten metal. The tempera-, Fig. 3 is a vertical sectional view showing in ture of the molten metal may range up to 1200" F. further detail the parts above referred to in conin the case of processes for detinning molten lead. nection with Fig. For the stirring apparatus impellers rotating at Fig. 4 is a bottom view of the parts shown in speeds up to 1800 R. P. M. may be used. Con- Fisand sidering the weight or the molten metal and the Fig. 5 is a perspective view of a stabilizing deinertia of the circulating streams thereof, it has vice in accordance with this invention, shown fore been found very diflicult to provide a detached from the other rotatable parts of the durable and rugged stirring unit which will withstirring apparatus.

stand these severe conditions. One of the seri- Referring how 8- kettle 15 indicated at 15 ous difliculties resides in the provision of suitable 0 containing a d of molten ta H mpr smeans for supporting the rapidly rotating stirring 8' for example, molten lead, which is being subunit in the presence of the heavy moving masses iected to a process" i o v rap d sti r A of molten metal in such manner that certain mas of dross which is separated from the molten so vibrations will not become soseriousastoquickly metal is indicated at ii. The kettle may be destroy the rotating parts and the supports theremounted as shown in a suitable fire box and for. That is, if an impeller is mounted on a shaft heated by oil or gas flames as at H. extending down into the molten metal, it is difli- At the top of the kettle a suitable frame work cult to provide a bearing for the lower portion of may be provided as at M for supporting a motor the Shaft w c will withstand the conditions I! having its shaft detachably coupled as at it 25 present. Accordingly it has b en attempted to with a shaft H. The shaft l1 may extend downsupport the shaft by providing the Journals or wardly into the molten metal and the greater bearings therefor at its upper end or above the portion o the S y be covered and p molten metal. But this practice leaves the lower tected as by a sleeve I8 against deterioration in end of the shaft relatively free to bend or vibrate e p se c of the high temperature metal. and 30 in di directions, thereby permitting, at high against abrasion due to the presence of the dross. speeds, a whipping action at the lower end of the Suitable bearing of 101111151 means y be p shaft which seriously increases the wear and vided, water-cooled if desired, as at II on the teanon all of the rotating parts and bearings, frame work l4.

a5 necessitating replacement of parts within a few At the lower end of the shaft a rotatable imfly peller as at It may be fixed as by key 2| and set The objects of the present invention therefore S ew 2|. The impeller of the form shown is so include the provision of means for stabilizing the shaped that up rapid turning of the Shaft by rotating parts of stirring apparatus of the chart e motor, the molten metal will be caused to 40 acter above referred to. Various further and rapidly circulate in paths such as indicated gen- 40 more p ific objects, features and advantages erally by the arrows in Fig. 1. will clearly appear from the detailed description Heretofore with impellers thus mounted on the given below taken in connection with the aclower end of a vertically extended shaft rotating p y n drawing which forms a part of this at high speed in molten metal, the currents of specification and illustrates merely by way of exthe molten metal have been such as to soon set 45 91 a preferred form of the apparatus of the up progressively increasing and powerful whipinvention. The invention consists in such novel ping effects at the impeller, i. e., vibrations of features, arrangements and combinations of parts the lower end of the shaft radially and about the as may be shown and described in connection axis. with the result that the shaft may soon 5c with the apparatus herein disclosed by way of become bent and jam, the bearings therefor are p destroyed, and all rotating parts are subjected In the drawing, Fig. l is a vertical sectional to excessive wear. The diillculty'of providing any view showing a kettle of molten metal incondependable bearing means at the lower end of nection with which stirring apparatus in accordthe shaft capable ct withstanding the conditions ance with this invention is mounted. present, will be quite apparent. as

It has been found, however, that the lower end of such a shaft may be stabilized to a surprising degree against such whipping effects by providing a coaxial extension for the lower end of the shaft, as for example in the form of a cylinder as indicated at 22. The cylinder 22 is preferably, although not in all cases necessarily, made hollow as shown. With a hollow cylinder the results are considerably improved over the results obtained with a solid cylinder. This cylinder may be attached to the lower end of the shaft as by means of a collar 23, the collar in turn having a xey-' way 24 for receiving the lower end of the abovementioned key II. The cylinder and collar may be secured in respect to the shaft and a set screw 24.

Although we have not precisely determined in all respects the manner in which this cylindrical extension operates so effectively in stabilizing the lower end of the shaft, it is believed that there may be a number of factors involved. Thus it will be noted that this extension presents an extended surface of revolution providing a bearing surface against the surrounding stream or streams of molten metal as drawn upwardly into the impeller. That is, above the impeller there will be a downwardly flowing movement of molten metal toward the impeller; the vortex created by the stirrer being more or less filled with dross as indicated. Beneath the impeller the movement of lead is symmetrical about the shaft axis, whereby the cylinder 22 has forces exerted upon it equally from all directions and as a result it exerts astabilizing force on the shaft. In view of the inertia of the heavy moving streams, the cylindrical member may therefore act somewhat as a bearing despite the absence of any fixed journal. Also the cylindrical member, if made hollow as preferred, will contain a substantial mass of the heavy molten metal, which in the case of lead will cause the extension to have a considerable inertia, that is, much greater than if the cylinder were of solid iron or steel. This may tend to dampen the vibrations and whipping effect. Also the rising and swirling current of heavy molten metal which engages and enters into and also surrounds this cylindrical member, may be so modified by the presence of this member as to tend to check or neutralize forces causing wobbling or whipping of the impeller. Also a swirling current of the molten metal may to some extent be established within the lower open end of the cylinder and out of phase with the swirling current outside, in such manner as to tend to neutralize the whipping action. In addition to all these effects the static head of lead (which as a solid, has a specific gravity of 11.37) exerts a stabilizing pressure onthe extension.

With an impeller of the type shown in the drawing and having a diameter of from 9 to 12 inches and mounted about 2 feet below the bearing on a 2V inch shaft, it has been found that the cylindrical member 22 will give a. surprisingly effective stabilizing eflect if made in the neighborhood of 4 to 6 inches in diameter and.10 to 12 inches long. However, these dimensions are given simply as illustrative of a preferred example andit is to be understood that the invention as hereinafter claimed is not to be limited thereto. The cylinder may for example be made of a section of relatively rigid machined steel tubing, preferably for best results, somewhat larger in diameter than the impeller shaft.

The effectiveness of the invention may be appreciated from the fact that with a typical high key as by speed installation before applying the above described device, the shaft, other ro-. tatingpartsm-bearingoftenhadtobereplaced after about three days of operation. On the other hand, with the application'of the above described stabilizing means, mechanical difficulties were substantially eliminated and the apparatus was made capable of substantially continuous operation for a number of months without repair or replacement of parts.

While the invention has been describedin detall with respect to a particular preferred example, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired .to be secured by Letters Patent is:-

1. In apparatus for stirring molten metal, a rotatable shaft for extending downwardly for a substantial distance into the molten metal, Journal means for said shaft, the Journal means being located above the molten metal, an impeller within the molten metal and fixed to said shaft, said impeller being so shaped as to cause molten metal to be drawn upwardly to the in peller and thence outwardly therefrom, the end of the shaft within the molten metal being unsupported by any bearing structure, means at the upper end of the shaft for rotating same at speeds such that the lower portion of the shaft is subjected to forces tending to cause destructive transverse vibration and bending thereof, and means on said shaft below said impeller for stabilizing the lower portion of the shaft against such vibration and bending, said means comprising an enlarged coaxial extension for the lower end of the shaft, formed with a surface of revolution extending to a substantial distance below the impeller and presenting extended bearing. areas against the surrounding stream of molten metal as drawn up- .wardly to the impeller.

2. In apparatus for stirring molten metal, a rotatable shaft having a free end extending downwardly for a substantial distance into the molten metal, an impeller within the molten metal and fixed to said shaft, means at the upper end of the shaft for rotating same at speeds such that the lower portion of the shaft is subjected to forces tending to cause destructive transverse vibration and bending thereof, and means on said shaft below said impeller for stabilizing the lower portion of the shaft and impeller against such vibration or bending, said means comprising a coaxial extension for the lower end of the shaft, formed with a surface of revolution extending to a substantial distance below the impeller and presenting an extended bearing surface against the surrounding streams of molten metal.

3. In apparatus for stirring molten metal, a

rotatable shaft having a free end extending downwardly' for a substantial distance into the molten metal, an impeller within the molten metal and fixed to said shaft, and means on said shaft below said impeller for stabilizing the lower portion of the shaft and impeller against radial vibration, said means comprising a coaxial extension fixed to the lower end of the-shaft, such extension being a hollow cylinder open at its lower end.

4. In apparatus for stirring ,molten metal, a rotatable shaft having a free end extendingdownwardly for a substantial distance into the molten metal, an impeller within the molten metal and fixed to said shaft, and means on said shalt below said impeller for stabilizing the lower portion of the shaft and impeller against radial vibration, said means comprising a coaxial extension for the lower end of the shaft, formed with external and internal surfaces of revolution, both of said surfaces contacting with the molten metal.

FRED R. MULLER. WALTER T. MONSON. 

